/**
*      author: Y_Yao
*      created: 2025-01-24 22:03:39
**/

#include<bits/stdc++.h>

#define int LL
using namespace std;
using LL = long long;
const LL LLINF = 1e18;
const int INF = 0x3f3f3f3f;
const int N = 2e5 + 7;
string s;
int n;

void solve()
{
    cin >> n;
    cin >> s;
    int ans = 0;
    for(int i = 0;i < (int)s.size() - 1;i++)
    {
        if(s[i] == '#' && s[i + 2] == '#' && s[i + 1] == '.')
        {
            ans++;
        }
    }
    cout << ans << endl;
}

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);

    int t = 1;
    //cin >> t;
    while(t--)
    {
        solve();
    }
    return 0;
}